package com.mxb.sqlsession;

import com.mxb.model.Configuration;
import com.mxb.model.MappedStatement;
import com.mxb.utils.GenericTokenParser;
import com.mxb.utils.ParameterMapping;
import com.mxb.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * 类描述
 *
 * @Author: MaXiaobing
 * @Date: 2021/3/9 21:41
 */
public class SimpleExecutor implements Executor {
    @Override
    public <T> List<T> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {

        // 1、注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2、获取sql语句
            // 1)将#{}转换为？ 2)存储参数名
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3、获取预处理对象preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4、设置参数，获取入参对象的全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);    // = user对象
            preparedStatement.setObject(i + 1, o);
        }

        // 5、执行sql
        ResultSet resultSet = preparedStatement.executeQuery();

        // 6、封装结果集
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        List<Object> objectList = new ArrayList<>();
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            // 元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段值
                Object value = resultSet.getObject(columnName);
                // 使用反射或者内省，根据数据表和实体的对应关系完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objectList.add(o);
        }
        return (List<T>) objectList;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, Exception {
        // 1、注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2、获取sql语句
        // 1)将#{}转换为？ 2)存储参数名
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3、获取预处理对象preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4、设置参数，获取入参对象的全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);    // = user对象
            preparedStatement.setObject(i + 1, o);
        }

        // 5、执行sql
        int rows = preparedStatement.executeUpdate();
        return rows;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null) {
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        } else {
            return null;
        }
    }

    private BoundSql getBoundSql(String sql) {
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }
}
